The present invention relates to heat exchanger arrangements, and more particularly to a method of monitoring a heat exchanger arrangement for excessive pressure drops that may lead to a stall condition.
Motor assemblies utilizing ram air flow are employed in a variety of applications, with one such application being an aircraft. The ram air flow in an aircraft may serve various purposes, such as in cooling systems for the aircraft. For example, the ram air flow may be utilized to remove heat from various aircraft systems and/or be used to condition aircraft cabin air through a heat exchanger arrangement. When the aircraft is in flight, the movement of the aircraft creates a sufficient source of ram air flow which can be used for the purposes described above. When the aircraft is on the ground or is operating at low speeds, however, a ram air fan is typically utilized to supply air flow to the cooling systems. Over time, contamination from ambient air will increase the pressure drop of the heat exchanger arrangement, thereby reducing flow through the ram air fan and heat exchangers. Significant heat exchanger contamination may reduce the airflow to the extent that the ram air fan operates in an unstable operating mode, such as a stall condition, which may cause excessive blade stress resulting in a failure of the ram air fan.